1. Field of the Invention
The present invention relates to surgical staples and to a method and an apparatus, particularly an anvil for a surgical stapling device, used to deform such staples to secure adjacent layers of tissue together. More specifically, this invention relates to the configuration of malleable, bioabsorbable, plastic or polymeric staples for suturing body organs and tissue, and to a precision-formed anvil for deforming the staples into that suturing configuration.
2. Description of the Prior Art
Historically, suturing of a surgical or other wound in organs and tissue has been done by hand. Conventional hand suturing techniques require a high degree of surgical skill. However, expertise in such techniques can vary widely from surgeon to surgeon, thereby resulting in widely varying quality in performance of the concluding steps of an operative procedure. In addition, even very skillful surgeons require a considerable amount of time to suture even relatively small wounds. Therefore, it is possible that an undesirable amount of blood may be lost during the suturing operation.
Accordingly, there has been an increasing tendency in recent years to use surgical staples to suture body organs and tissue after a medical procedure. Surgical staples have been particularly effective in suturing body organs and tissue such as the lung, as well as the esophagus, the stomach, the duodenum, and other body organs in the intestinal tract.
The advent of surgical stapling has provided several marked advantages over known hand suturing techniques. First, since one or more rows of surgical staples are inserted into tissue using a specially adapted instrument that is simply actuated, near uniformity of the closure from one surgeon to the next results. In addition, all staples in the closure are usually inserted simultaneously or in rapid sequence across the entire wound. Therefore, the closure is made very quickly to minimize loss of blood.
Surgical staples are usually mechanically inserted into tissue with surgical stapling instruments such as those known as anastomosis devices, including gastrointestinal anastomosis devices and transverse anastomosis devices. In such devices, the staples are loaded in one or more elongated rows into a magazine or cartridge. The magazine is then mounted in the device, which includes a mechanism for pushing, or driving, the staples from the magazine through two or more sections of tissue toward a deforming anvil. At the conclusion of the driving operation, the legs of each staple are conventionally clamped or bent, by engagement with the anvil, to a closed configuration to complete the suture and join the tissue sections together.
Gastrointestinal anastomosis-type devices drive and bend the staples aligned in a row one after the other in rapid sequence. Transverse anastomosis-type devices drive and bend all staples in a row simultaneously.
One type of conventional staple 10, shown in FIG. 1, used with both gastrointestinal anastomosis and transverse anastomosis-type surgical stapling devices is made of a metal, like stainless steel or titanium, that is substantially inert in the body. The undeformed staple 10, or staple blank, is generally U-shaped and includes a back span 12 and two legs 14 depending perpendicularly from the back span in parallel to one another. Each leg 14 has a sharp chiseled end point 16 for cleanly piercing body organs or tissue. The metal staple blank is bent by having the legs engage and follow a conventional anvil to form a B-shaped closed staple 18 as shown in FIG. 2.
The anvil used to bend metal surgical staples is also formed of a hardened metal and includes a staplebending face having a pair of coined or punched pockets located to oppose each staple in the magazine of the stapling device. The pockets are ordinarily elongated arcuate depressions, co-linearly arranged in parallel to the back span of a corresponding staple held in the magazine. Thus the anvil closely resembles the anvil of a conventional paper stapler.
When the staples 10 are driven from the magazine toward the anvil, the staple legs 14 each engage one pocket so that both legs are bent toward each other initially and thereafter upwardly toward the back span 12. Thus, as shown in FIG. 2, the end points 16 may come to rest against the underside of the back span 12.
Although metal staples inserted in the manner described above provide an effective and relatively simple means of suturing, one significant disadvantage is that they remain in the patient's body permanently. While generally not injurious to the body they may nevertheless interfere with post-operative X-ray or other diagnostic imaging of the patient.
This disadvantage can be overcome by using bioabsorbable polymeric staples that are degradable in the body after a short period of time. However, conventional polymeric staples are not malleable and thus cannot be easily bent into the B-shaped configuration shown in FIG. 2, to complete a suture. Therefore, as shown in FIG. 3, such conventional bioabsorbable staples instead are made in two parts, namely a U-shaped polymeric staple body 20, the legs 22 of which are joined by a polymeric bar-like closure 24. The closure has two end point-receiving holes 26 that fit over the end points of the staple body 20 after they have pierced the tissue to be sutured. The staple body 20 and closure 24 are then forced toward each other to complete the suture.
While this two-part staple will dissolve in the body and, therefore, does not interfere with post-operative procedures, it has the drawback of requiring a part in addition to the basic staple blank and thus requires a more complicated mechanical stapling device for properly aligning the two parts and driving them together.
More recently, the assignee of the subject invention has made a breakthrough in the bioabsorbable staple field. Specifically as described in U.S. Pat. application Ser. Nos. 07/548,802, now U.S. Pat. No. 5,080,665, and 07/548,803, both filed Jul. 6, 1990, and U.S. Pat. application Ser. No. 07/799,521, filed Nov. 27, 1991, which are incorporated herein by reference, bioabsorbable or partially bioabsorbable surgical staples have been developed using polymeric materials. (Hereinafter the term "bioabsorbable" will be used generically to describe surgical staples of the type described in both of the applications mentioned above.) These staples retain all of the beneficial attributes of known bioabsorbable staples, but in addition are malleable or plastically deformable like metal staples. That is, these staples may be bent into complex shapes that are then retained. Therefore, they may be made of a single piece, not requiring independent staple body and closure parts.
Nevertheless, it has been found that if these new bioabsorbable staples are bent in the same way as are conventional metal staples, as shown in FIG. 2, so that the chiseled end points of the staple legs hit the back span, the points may crush or break.
Therefore, improvements in surgical staples and devices for inserting them, taking advantage of the attributes of the new polymeric materials described above, are desirable.